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valley996

Casper Labs Ceramic IMS Bearing

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It is probably inevitable that we will have to make studs for those customers that have damaged theirs. Porsche does not sell this detail part. Right now, the only change we plan on incorporating, is putting in a recessed hex (like a socket set screw) instead of the screw slot. These will be expensive for what they are. The hex will be plunge EDM machined, and will require a lot of machine time. Domestic maching cost is at an all time high. Grinding two diameters won't help.

All these anerobic resin sealants are miracle products when used properly. If they get into an open bearing, they can be death. While the stuff could salvage an out of limits IMS bore (rare), the other consequences are unacceptable (high removal forces, contamination). The only location using them with our procedure is on the three 6mm screws holding the support in the case (blue thread sealant). When you are installing with tapping action, the stuff could splash everywhere.

Like all things Porsche, this requires a special tool. You can't hold the stud with screwdriver, and tighten the nut with a conventional torque wrench. We get around it by taking an inexpensive beam type torque wrench, and boring a .250 hole thru the head for the screwdriver. If you use a .5 square drive torque wrench, there will not be

enoungh material removed in the critical area to upset the calibration of the wrench at these low torque levels. Yes, Porsche spec for nut torque.......period!

We recommend using a new OEM stud clinch nut for every final assembly. The thread running forces can drop after one use and reduce the clinch feature.

It would be curious to know if LN pulled the cage and dismantled the old bearing for inspection before recommending replacement. Anybody who is serious about bearings has a magnifying right angle scope that you plug into the USB on the computer. If there is no damage to a bearing (even a $5 bearing), there is no excuse for not reusing. I can take a pick of any feature and email it to the eng. rep at the brg mfgr..

BR

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The tool I made was a 12 point deep socket, hollowed out to accept a slotted screwdriver. Then ground two sides down flat to fit a crows foot so I could use the "# square drive torque wrench. I'm pretty convinced the nut was so terribly difficult to remove from the use of the green loctite. I think during re-assembly, I will either use a very tiny dab of this or none at all, since it sounds like the entire point of the nut is just to draw the tube into the flange (real support) at the correct depth.

LNE did not disassemble the bearing, the inner race was found to have a small amount of play outside of tolerance, perhaps damaged during extraction or insertion. Once they got that far in the analysis I don't think they went any futher.

Edited by logray

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If the nut is over torqued, you run the risk of tensile failure just as you as described. When the stud breaks, the IMS is free to shuck back and forth in the case (that was the noise heard). Since the stud does nothing to support the bearing (just sets the running position) there was no reason to cause bearing damage. The stud's nut is a clinch lock type, and you hold the stud from turning with just a blade screwdriver after the nut is started. The little screw slot's anti-rotation role in tightening the nut should tell people "whoa, why is this here?" And,.....is one reason why the torque spec for the nut is so low. This is why we make a big, bid deal about procedures. I understand your concern, and take your comments seriously. Barring a defect in the original part (which is possible but not likely, and can occur regardless of size) the only scenario that can fail the stud is overtorque. You would think that the limit of holding the screw slot with a screwdriver would limit the installed torque. But in practice, once the nut starts an axial load on the stud, you don't need to hold the slot in position any more on many of these engines. Some turn, and some don't w/o the screwdriver in place. This is what makes the "tweaking" possible. Nobody likes tasks that are awkward or difficult. Learning the technique to hold the slot and tighten the nut takes practice, and I understand why you guys don't like it. But it was done for a reason.

The OEM stud actually has a couple advantages over a "beefed up" stud. 1) If things don't go together right, it limits the load you can put on the inner race. When you are

pulling on the inner race, it creates a load path thru the balls. Remember the discussion yesterday about bearing design for radial only loads. If you pull too hard, the races can get indented from the balls, and they are ruined. 2) The more material that goes into the stud dia., the less available to actually support the bearing ID. If the support flexes, it won't be long b4 other problems start.

While on the subject of odd ball failures............. When you guys come across strange failure modes, we would love to see the parts. Send them to us, or give us a call.

We can look at them in the lab, and tell a bunch of things not apparent to the naked eye.

BR

Casper Labs, Inc

You might be interested in the fact that the center bolt failure we saw was not the only one we are aware of, there have been at least two or three more, all were factory engines that had never been apart. Two of the bolt failures involved bearing failures as well the the center bolt, all of which failed at or very near the under cut area. I am not aware of any of the LN style center bolts failing, even on the very small number of bearings that have had problems.

Edited by JFP in PA

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...The only location using them with our procedure is on the three 6mm screws holding the support in the case (blue thread sealant)...

Interesting. So then your not recommending flange sealant around the perimeter of the flange seal, flange sealant on the base of the bolts or nut, or use of factory ordained micro-encapsulated bolts from Porsche?

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JFP,

Once the bearing fails, all bets are off on the stud. The stud was not designed to take any radial load (which it will when it the bearing clearance opens up and it starts shaking). This is not a chicken or egg situation. LN claims their beefed up stud helps keep it together after the bearing dies. Well,..........you still got the same problem.

Dead bearing. Our objective is to never fail a bearing.

Nor Cal,

Your statement is 100% correct. You can use new encapslated 6MM bolts or the old ones with blue loctite. Same thing...thread sealant. Gasket cements by any name are

crutches to seal less than ideal mating surfaces. On precision fitting parts (like o-ring seals), you run the risk of deforming or locking in place (after it sets up) a rubber seal that was designed to seal thru flexibility (accomodates engine thermal growth and vibration). If you have a beat up surface, then you have to use some judgement as to what sealer to help seal the gouges. In this hardware, there are not a lot of ways to beat up the sealing surfaces. The original black o-ring seal support was pretty marginal because the ring was small x-section. The late 3 rib types are very reliable. But ..........some of you guys really like sealants. That is our position. If we design a sealed joint for any of our customers, we will not accept any design that requires sealants (except direct metal to metal interfaces,....like a crankcase parting line) .

BR

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Bill-based on the complete answers you have provided it is obvious (to me) that you have given this engine a lot of thought .In one of your ealier posts you mentioned that that the cylinders might benefit from some old fashion technology -cast iron sleeves .My research leads me to the opinion that this is a viable solution .However there is one doubt and that is the different expansion rates of the sleeve and the block .I know that the heat transfer would suffer -something like 7% which I don't think is a big issue .

As a footnote I resleeved a 235 hp outboard and it worked fine .So in certain cases cast iron and aluminum do mix .

Would you mind sharing your thoughts ?

Dave

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logray,

Your prior statement, " it sounds like the entire point of the nut is just to draw the tube into the flange (real support) at the correct depth." is an important one for the readers, as it could be misunderstood. The stud should never be used as a puller unless you are removing the bearing. Its purpose is to lock the ID bearing race up against the vertical face of the support. If you have not relaxed the tension in the drive chains by setting the correct crank position, removed the hydraulic tensioners, AND rocked the crank back and forth, the bearing will be subject to a radial load that is significant. When you are just removing the support, this radial load can make the support seem like it is locked in. Some mechanics just can't figure out how to get the support out when this happens. The ID fit of the bearing to the support is loose, it should slide right in.

BR

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...The ID fit of the bearing to the support is loose, it should slide right in...

This is getting more interesting by the hour. I have found the center support on the LNE bearing to be slight interference, requiring some force to insert into the bearing (although they ship already pressed in). Yet the flange to outer race seems to not be as tight a fit, but still very tight - able to be pressed in by hand - probably less than 0.001" for both my guess.

To expand on the role of the center support and "draw in" comment I made. As I'm assembling my engine after a Nikies rebore, the IMS tube literally FLOATS around both bores, axially and radially, especially if the oil pump console is removed, and of course certainly without any chain tensioners installed. Once the oil pump console is installed, it floats considerably less radially on the flywheel side (and just a few thousanths on the pulley side), but still floats axially until the flange is installed.

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dcdreschsel

You just can't consider an open deck engine a serious performance engine because of the issues mentioned. If your performance expectations are modest, go ahead and sleeve it with iron. There are probably a million Subarus out there with this design (I have one). There is one case where Subaru copied Porsche (not the other way around, as you have probably heard), the 3 ply head gasket. It solved leak issues they were having, and is very forgiving of thermal movement.

Sleeving outboads is incredibly common here in FL. There are some things to watch carefully when sleeving, the bore out has to be smooth and uniform diameter top to bottom. (This requires flood coolant during the boring/honing). Follow the sleeve makers interference fit and assembly recommendations exactly. When you heat the case, put a thermocouple as close to the cylinder as possible (it takes longer to heat a case than you think). And be sure to measure the bore after heating to make certain you have about .008" clearance when you drop in the sleeve.

Sleeving should not be considered a last resort repair procedure, it is a primary design feature. In sea water outboards, you can set up a galvanic reaction between the iron and aluminum if they are not in intimate contact. The sleeve makers will tell you to coat the sleeve with Loctite 620 before insertion. Between the interference fit and the 620 there won't be any gaps to cause this problem.... even in outboards, never mind Porsches.

BR

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Logray,

Now you are getting into another area that explains why I want trained/equipped people doing the kit install. As part of the instructions, there is a table of fits and clearances. You really should have ID and OD micrometers that read in tens of thousandths to measure everything before you start beating a bearing with a hammer. Mics like these are not common in a typical garage. Usually only wrist pins and ball bearings require this close measurement. It is not absolutely a requirement, but it is highly recommended. Either your parts are deviated, you have mis-measured , or LN has redesigned the OEM fits. In order to remove or install the the support (on engine servicing) the ID race MUST be a loose (no slop, but rather a sliding fit that would drop in of its own weight if layed on the side) to the support (to prevent loading thru the balls and potentially damaging the bearing with an axial load). This is a key design requirement. The OD is a light tap interference fit. If it does not require force, it is too loose. You can not rely on the snap ring to retain the bearing. We are seeing some variation in the OD brg fit of the sprocket hub. The bearings are dead nominal, its all in the hub.

BR

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...no slop, but rather a sliding fit that would drop in of its own weight if layed on the side...

At what ambient and material temperature are these properties observed, kind sir? From my observations, even the extracted stock ball bearing and it's center support simply did not exhibit the "loose fitting" qualities you describe. Does your after-market bearing exhibit the qualities you extrapolate henceforth?

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It does not matter what temp the housing and bearing are, AS LONG AS THEY ARE BOTH AT THE SAME TEMPERATURE WHEN MEASURING. Remember, you are subtracting ID from OD, its only the difference between that matters.

As stated in #82, if all the side loads from the chains are not relaxed, the fit will feel tight. Once you get the support out, look at the end of the IMS. Is it precisely centered in the slightly larger case opening? Can you put your finger on the end of the stud and gently rock the IMS left to right? If the answer to either is "NO", you have not completley relaxed the chain tension, and there will be drag on the fit.

Now, lets say you split the case with an intact IMS brg and support assy. You take it to the bench and remove the nut. You grab the support and it won't just slide out. Happens a lot,........why? You figure out a way to pry or push on it until it comes out, does not take much,.....but it is not loose. Hmmm,..........you notice a slight brown film on the surfaces. Take some carb cleaner and a rag and wipe/wash until the film is gone on both parts. Ahhhh, it now slides right in like Bill says. What is happening? When you have a fit that is right on verge of line to line, anything that gets in locks it up.

This is a really big problem in aircraft piston engine cam followers, which have a similar sliding fit to the case (cam in case OHV engine). A lot of these engines sit for months w/o running. When the owner finally comes out and starts it, the lifter is varnished. The cam and valve spring push it back and forth, but it no longer wants to spin, so it wears on one spot. Eventually, the cam goes round. This is a lesser problem w/ the Porsche because the oils are superior (it is a big deal to get an FAA certification for new lube chemistry, and the sales volume low. A/C piston engine oils typically lag the car oils by a decade in sophistication).

Every support we have seen in this study (that has not been mechanically damaged) has exhibited this sliding fit when cleaned up.

BR

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A correction to an earlier post I made. The torque spec on the center lock nut is NOT 25 ft lbs.

If using the LNE kit and instructions, do not exceed 24 ft lbs, but that doesn't mean TORQUE to 24 ft lbs. LNE recommends the FACTORY spec for torque.

The factory spec is 8 ft. lbs when using the factory center stud tool. HOWEVER I've seen 10 and 12 ft lbs online as well (both without the factory tool).

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There are a lot of tightening "specs" floating around on these engines. Going back to Porsche's 1996 approach (early design), the only torque values used were initial values to "set" or flatten gaskets before going to the final compressive load by "angle of turn" (to a ridiculous + or - 2 degrees in the OEM manual). The angle of turn method gained big momentum years ago, when the US military was looking for a way for mechanics to reliably tighten hardware in the field under less than ideal shop environments. As you all know, the amount of load on any screw fastener can vary greatly with lubrication, thread condition, etc.) It is a great deal easier to reliably set the preload on a large diameter/very short lenght fastener by angle of turn, than on a long, slender one. So, the Navy mechanics fixing a 9" battleship cannon have a lot fewer issues with "angle of turn" than Army helicopter mechanics.

The average auto mechanic has neither the time or patience for angle of turn. You have to get all the oil off the fastener head, and some how mark it. (How do they achieve + or - 2 deg. accuracy on a 6 or 8MM fastener?) . He wants to grab his 6% accuracy click type torque wrench, and yank on it. You really cannot blame him. Fortunately there is enough design margin on most fasteners, that everything works out OK.

I was hoping to avoid this post for fear of diverging into this contentious torque issue. The point of my prior post is that this 8mm stud has only one role in the bearing design, to set the axail running position of the bearing/ IMS. Again..........there are no axial loads imparted on the IMS from any source. If you took a plain nut, threaded it finger tight with the ID race up against the support, and had some miracle "glue" to hold the nut from loosening............it would fullfill all of its design job requirements. Forget about the nut torque (for now) for the purpose of understanding how the IMS design wiorks.

Since the OEM nut is a clinch lock type, there is no need to use Loctite. Do you wear a belt with suspenders? In fact, the Loctite acts as a lube, slightly altering the preload at constant torque. But, much worse could happen. If the stud threads get really goobered up with loctite, and it runs down the stud to the O-ring,................ it will lock up the O-ring. Loctite type compounds in an o-ring groove will cause leakage every time.

I know this sound like heresy to some of you,.... sorry.

BR

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I would like to thank BR of Casper labs for providing all of us with a large amount of information. If anyone uses his product please provide us members with some feedback. Like I said I will be doing my replacement this Spring and I will certainly give Casper some consideration. Thanks again for an interesting thread.

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Valley996,

When we decided to go forward with this project, we were well aware that the years of unresolved issues surrounding the IMS were going to present a challenge (to overcome ingrained perceptions, doubt, and poor Porshe product support). The automotive market is a lot different from other markets we serve, because it relies so heavily on word of mouth reputation (as apposed to regulatory agengy approval for product endorsement). When you come in and say, " This does not need to cost so much!". People think, "cheapo version". It is going to take time for the misconception to right itself.

This thread has been helpful to us in figuring out how to give all of you the information you need to understand everthing we discussed (as well as our ad info). We think the best way to go from here is by making a web accessed .pdf file of the installation manual, as well as some You Tube videos. The links to these will be posted on a later reply to this thread.

We have had a few highly specialized Porsche products on the market with Wayne Dempsey since 2004. Like the IMS bearing, we came up with a metalurgical fix for the infamous 911 head stud. Thousands of these have been in service since 1993, and have never, ever, had a failure. We have seen studs that looked like they were installed with a pipe wrench and four vice grips, and they never fail. One of the top 911 engine variant builders in the USA uses these studs exclusively (and sells they under his brand name by agreement with us). Ask Wayne if he has ever had a report of a product failure on even one of our parts. People pass over the stud in the catalog every day because they are 30 to 40 per cent less than the highly (and expensively) advertised studs made by others. "Those can't be any good at that price!"

Some of those other aftermarket studs are made of material designed for 400 deg F max service. Since the CHT frequently exceeds this even on a street engine , They fail right where the stud passes into the head after about 100hrs of thermal transients.

The good news is, we put another six of these beaings on the road in the last two weeks. This is going to be an interesting project (and a challenge) for a while. Like Wayne, I return all emails and phone messages (if not immediatly available). N1WR@juno.com or 561-575-3157 (9a-5p ETZ)

Regards,

BR

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A suggestion for your product. You might want to consider selling or suggesting a tool to use in order perform the center nut torque (aimed more at the DIY individual than a pro shop). I'm not sure why LNE doesn't do this, since they already make and sell a variety of specialty tools, and this is one job that I think warrants a special tool. OF course, professional shops will probably have thru hole socket set or perhaps the factory tool already.

Granted your design uses the standard center locking bolt, for the LNE center nut which is 12 point, I used this tool a couple days ago on my engine build and it worked extremely well. As I posted above, it is just simply a hollowed out 3/8" drive 12 point deep socket. This way I can fit a variety of sizes of screwdrivers into the stud. The sides of the socket are flattened out to accept a crows foot, which can then be torqued using the inch pound torque wrench. I didn't have this tool the first go around at bearing installation and this second time I felt much more confident with the installation (oh and it helps that the engine is out of the car, much less cramped).

IMG_4764.JPG

(click to enlarge)

Edited by logray

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We have given that some thought. The 12 point nut LN uses is a standard aircraft product. Very good quality, available in "inch" dimensions only, and strictly one tightening cycle. Anyone who uses these nuts,immediatly picks up on how well they support the socket, there is very little socket rock. It is hard not to like them. The problem is the screw slot. As you say, the tightening process is not easily coordinated, as the screw blade wants to twist out of the slot.

It is easiest to do this tightening if two people do it. One concentrates on holding the the screwdriver in the slot both axially and in torsion. The other turns the torque wrench. If you go to the recessed hex instead of a screw slot, it gets much easier. The allen wrench does not have the problem of twisting out, so one person can do the tightening easily.

When you get to the tightening specs for small fasteners, you find there is usually big margin. Since the nuts used in this app are prevailing torque (clinch) types, you don't have to worry about thread distortion under torque to prevent loosening. The distorted nut does the locking. Since there is no design axial load on the IMS, now you have a lot of flexibility. Fortunately, torque is not very critical here. You just have to find a way to keep people from grossly over torqing (that leads to a broken stud/nut rattling in the bell housing). Expect we will offer some low cost beam type torque wrenches with a hole thru the square drive (or make your own). The more adapters, crows feet, etc. you add to the wrench,....the more calibration accuracy lost. Keep it simple.

BR

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I have a huge bin full of old screwdrivers I've collected over the years and found one that fits very snugly in the center stud. Your average "ye' olde' shade tree" might just pull out "screwdriver of size X" and put it in there and say "good enough". I can't emphasize enough how confident I felt while tightening this hardware. It offered very little play or resistance, and once the click stop wrench provided it's feedback, I knew that enough was enough, and cracked open an ice cold soda pop for celebration.

I think you might have mentioned in an above post you would offer an allen/hex option instead of the slotted end of the center stud. An allen wrench would seem to make a whole lot more sense. And great idea on the two person job...

I tried to keep the adapters to a minimum, it's just a crows foot and the torque wrench. No extensions, size adapters, etc. etc. to change the specs signifigantly enough (although a slight calculation for the green thread locker).

As you pointed out the fit of the crasftsman socket to the fastener is more than superb and substantially adequate for the task at hand.

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Those 12 point nuts are categorized as "reduced diameter types". They can develop the full tensile rating of the male thread with much smaller OD. They use them for two primary reasons in aircraft. 1)They are lighter, and 2) they let you put more fasteners per square inch of space (stronger joints for a given area).

In the IMS they have only one disadvantage. Since the diameter is reduced, the socket size is small. Small sockets don't have much space for a nice wide screwdriver blade (and generously sized/twist resistant shank) that is resistant to coming out of the stud slot. That is why we use the Porsche nut, it is much larger diameter and customers are much less likely to have to bench grind the sides of the blade flats to get it to pass thru the wrench.

When we offer the replacement studs (for customers with damaged studs) we may go that route because the screw slot will be replaced with an allen type recess (and pass thru diameter concerns disappear). A box of 100 of the aircraft nuts can be had for about 15 to 20% of the unit cost of the Porsche OEM nut. So, at that point it makes sense.

BR

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Also, readers should note the photo in post #93. Every engine case should be this clean before removing the support. Do what ever it takes to prevent dirt and grit from getting into the new open face bearing when installing. Even light tapping of the bearing drift will dislodge particles if not removed before hand.

BR

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We toyed around with the "man invents tool" approach for this, then settled on using a crows foot at a right angle on an inch pound torque wrench for the nut (no torque setting adjustment required), and a slotted screw attachment adaptor to 3/8 ratchet drive (Sears) on the center bolt, which gives on person sufficient grip and leverage by simply using both hands. Never had a problem with this setup.

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The other advantage of the hollowed out socket is that it makes snuging up the bearing to the LNE installation tool a breeze.

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Every engine case should be this clean before removing the support.

I must confess the real reason why it is this clean. :)

IMG_4573.JPG

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